Chlortetracycline and related compounds (e.g., tetracycline, 6-demethyl chlortetracycline, 6-demethyl tetracycline) are widely used as antibiotics, additives to animal feed, and intermediates in the synthetic production of other antibiotic drugs. These compounds are typically produced commercially in submerged fermentation by Streptomyces aureofaciens. See, e.g., U.S. Pat. Nos. 3,005,023 and 3,019,173; Merck Index, Eleventh Edition (1989). Sophisticated fermentation techniques, media formulations, and high-producing mutants of S. aureofaciens have resulted in increased yields of chlortetracycline and its derivatives. See Goodman, Handbook of Experimental Pharmacology, 78:5-57 eds. Hlavka and Boothe (1985); Veselova, Antiobiotiki, 14:698-702, 1969. However, some derivatives can only be produced efficiently semi-synthetically.
Recently, recombinant DNA techniques were used to the isolate the gene cluster encoding the proteins responsible for the biosynthetic pathway for producing tetracycline, chlortetracycline, and other derivatives from S. aureofaciens (see, U.S. Pat. No. 5,589,385 to Ryan et al.). This genetic information is used in the present invention to produce genetically altered strains which produce high levels of a desired biosynthetic product.
Because tetracycline and its derivatives are such useful compounds, new selective, increased yield methods and vehicles for the preparation of one or more of these tetracycline compounds are desired.